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Dual Relay Board

ID: 3051_1

Mature: This product (or a similar replacement with a compatible form, fit and function) will be produced as long as the parts and components required to make it are available. It is estimated to be available for five years or more.

This board has 2 SPDT mechanical relays rated at 210W for DC or 1750VA for AC.

$19.00

The Dual Relay Board allows you to control larger loads and devices like AC or DC motors, electromagnets, solenoids, and incandescent light bulbs.

Note: This board is not suitable for switching signals. It takes at least 100mA of current to bridge the oxide layer that forms on the relay contacts, and most signals will not meet this requirement. If you need to switch signals, check out the 1017 - PhidgetInterfaceKit 0/0/8.

Connection

This relay board can be controlled with Phidget digital outputs. For more details, see the Connection & Compatibility tab.

Comes packaged with

InterfaceKits and Hubs

This board requires an analog port for power and a pair of 5V digital outputs to trigger the two relays. Below is a list of Phidgets that have both of these features. If you are planning on using a VINT Hub, you should buy two REL2001 boards instead of the 3051.

Phidget Cables

This board comes with its own Phidget cable to connect it to an InterfaceKit or Hub, but if you need extras we have a full list down below. You can solder multiple cables together in order to make even longer Phidget cables, but you should be aware of the effects of having long wires in your system.

Enclosures

You can protect your board from dust and debris by purchasing an enclosure. An enclosure will also prevent unintentional shorts caused by objects touching the pins on the bottom of the board or any terminal screws.

Connect the circuit to the terminals of the 3051. Connect one end of the series circuit to the 1C (common) terminal, and the other to either the NO or NC terminal, depending on what state you want the circuit to start in.

Connect the Phidget cable to the black connector on the 3051, and connect the other end to the analog input of the 1018. If you're using a non-Phidgets device, cut a Phidget cable in half, connect the red wire to a 5V supply, and the black wire to the ground. The white wire is not used.

Connect the control 1 terminal on the relay to the digital output on the 1018 using a piece of hook-up wire.

Connect the 1018 to the computer using the USB cable.

Now that you have everything together, let's start using the 3051!

Using the 3051

Phidget Control Panel

In order to demonstrate the functionality of the 3051, we will connect it to the 1018, and then run an example using the Phidget Control Panel on a Windows machine.

The Phidget Control Panel is available for use on both macOS and Windows machines. If you would like to follow along, first take a look at the getting started guide for your operating system:

First Look

After plugging in the 3051 into the 1018, and the 1018 into your computer, open the Phidget Control Panel. You will see something like this:

The Phidget Control Panel will list all connected Phidgets and associated objects, as well as the following information:

Serial number: allows you to differentiate between similar Phidgets.

Channel: allows you to differentiate between similar objects on a Phidget.

Version number: corresponds to the firmware version your Phidget is running. If your Phidget is listed in red, your firmware is out of date. Update the firmware by double-clicking the entry.

The Phidget Control Panel can also be used to test your device. Double-clicking on an object will open an example.

Digital Output

Double-click on a Digital Output object in order to run the example:

General information about the selected object will be displayed at the top of the window. You can also experiment with the following functionality:

Toggle the state of the digital output by pressing the button. This will change the relay state.

Technical Details

General

A relay is an electrically-controlled switch. Although many types of electrical switches exist, a relay's mechanical nature gives it the advantage of reliability and current-switching capacity. The main disadvantage to using mechanical relays is their limited life-span, as opposed to solid state relays who do not suffer from this drawback. For more information on mechanical relays refer to the Mechanical Relay Primer

Using a Digital Output Relay

Relays have a connection scheme determined by the arrangement of contacts within the relay. Because relays are a type of switch, they are defined in the same way other electromechanical switches are defined. In switch schemes, the number of poles represents the number of common terminals a switch has, and the number of throws represents the number of switchable terminals that exist for each pole. The relays used in the Dual Relay Board are SPDT relays: single pole, double throw. The internal construction of this type of relay is depicted in the diagram to the right. Many other types of relays exist: SPST, DPDT, and DPST, to name a few. In an SPDT relay, one of the throw terminals is labelled Normally Closed (NC), and the other is labelled Normally Open (NO). As the name indicates, the normally closed terminal is the terminal connected to common when the relay coil is not powered. When the relay coil is energized by the relay control circuit, the electromagnetic field of the coil forces the switch element inside the relay to break its contact with the normally closed terminal and make contact with the normally open terminal. The switch element would then connect the normally open terminal and the common terminal.

Using Relays as an H-Bridge to implement Forward/Reverse

Connect the load to the COM terminals, in this case the wires of a DC motor. The Normally Open (NO) terminals are connected to the power supply (VCC), and the Normally Closed (NC) terminals are connected to the ground (GND) of the power supply. Connect the Control pins to a digital output. You can toggle the corresponding output to switch the relays. Looking at the diagram, when LeftCtrl is enabled and RightCtrl is disabled, the current will flow from the NO terminal of relay K1 through the motor and into the NC terminal of relay K2. This will cause the motor to rotate in one direction. Similarily, if LeftCtrl is disabled and RightCtrl is enabled, the current will flow from the NO terminal of relay K2 through the motor and into the NC terminal of relay K1. This will cause the motor to rotate in the opposite direction. When both LeftCtrl and RightCtrl are disabled, both ends of the motor will be shorted to ground and no current will flow. When both leftCtrl and RightCtrl are enabled, both ends of the motor will be shorted to VCC and again, no current will flow.

Wetting Current

When a relay is in one switch position for a period of time, oxidation of the open contact(s) can occur. Depending upon the internal coating material of the contacts, oxide films of varying density will be displaced upon the surface of open contacts; this film acts as an insulator to current flow. When the relay is switched, a certain amount of current flowing through the contacts, known as the wetting current, is required to remove the film of oxides and ensure proper conduction. Because of this requirement, these relays are not reliable for signal switching. See the device specification on page 10 for detailed requirements.

Load Noise

If highly inductive loads are used with the Dual Relay Board, it is recommended that a noise limiting component be used to prevent damage to the device. An MOV, TVS diode, or kickback diode (for DC applications) shunted across the load will assist in dissipating voltage transients.

Phidget Cable

The Phidget Cable is a 3-pin, 0.100 inch pitch locking connector. Pictured here is a plug with the connections labelled. The connectors are commonly available - refer to the Analog Input Primer for manufacturer part numbers.

What to do Next

Phidget Programming Basics - Once you have set up Phidgets to work with your programming environment, we recommend you read our page on to learn the fundamentals of programming with Phidgets.

This device doesn't have an API of its own. It is controlled by opening two DigitalOutput channels on the Phidget that it's connected to.
For a list of compatible Phidgets with Digital Outputs, see the Connection & Compatibility tab.

You can find details for the DigitalOutput API on the API tab for the Phidget that this relay connects to.

Product Specifications

Physical Properties

Switch Type

SPDT

Switching Speed Max

20 cpm

Recommended Wire Size (Control)

16 - 26 AWG

Recommended Wire Size (Load)

12 - 24 AWG

Operating Temperature Min

0 °C

Operating Temperature Max

70 °C

Board

Controlled By

Digital Output (5V)

Current Consumption Min

14 mA

Current Consumption Max

180 mA

Supply Voltage Min

3.3 V DC

Supply Voltage Max

12 V DC

Electrical Properties

Dielectric Strength

1.5 kV AC

Contact Resistance Max

100 mΩ

Load Voltage Max (DC)

* 30 V DC

Load Voltage Max (AC)

277 V AC

Load Current Min

100 mA

Load Current Max (DC)

7 A

Load Current Max (AC)

12 A

Turn-on Time Max

10 ms

Turn-off Time Max

10 ms

*Note: Switching this relay at voltages higher than 30V will result in a reduced product lifespan.

Please Note: This relay cannot be switched at its maximum AC voltage and current at the same time. Ensure that total power of the load does not exceed the switching power for the relay. For example, you can switch this relay at 277V AC and 6.3A (1750VA), or at 145V AC and 12A (1750VA), but not at 277V and 12A (3324VA).

Estimated Relay Lifespan

The lifespan of the relays on this Phidget vary depending on how much current you're switching and whether it's AC or DC. The following graph illustrates the relationship between load current and relay lifespan:

The vertical axis is the lifespan of the relay (number of actuations) and the horizontal axis is load current in amps. As you can see, increasing load current from 5A to 10A can reduce relay life by more than half.

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Phidgets Inc.

We believe in getting problems solved quickly and projects finished on time. That's why we specialize in making affordable, easy to use sensors and controllers that require minimal electronics knowledge.

Phidgets Inc.

We believe in getting problems solved quickly and projects finished on time. That's why we specialize in making affordable, easy to use sensors and controllers that require minimal electronics knowledge.